Why exactly did you change your hard drive settings? Your initial problem was just a missing ntldr file. Nothing in the BIOS needed to be changed.
First off, reset your BIOS settings back to defaults.
You said you are able to boot to 98, but not XP. Try booting into 98 after resetting your BIOS settings to default. Then, put in your XP cd and go into command line. Find your NTLDR file on the cd, then simply copy it to the partition where XP is. If you're not familiar with DOS commands, let us know and we'll walk you through it in detail.